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  <title>预定义常量</title>

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</div><hr /><div id="outcontrol.constants" class="appendix">
 <h1>预定义常量</h1>

 <p class="simpara">
下列常量作为 PHP 核心的一部分总是可用的。
</p>
 <dl>

  
   <dt id="constant.php-output-handler-start">
    <strong><code>PHP_OUTPUT_HANDLER_START</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that output buffering has begun.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-write">
    <strong><code>PHP_OUTPUT_HANDLER_WRITE</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that the output buffer is being flushed, and had data to output.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-flush">
    <strong><code>PHP_OUTPUT_HANDLER_FLUSH</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that the buffer has been flushed.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-clean">
    <strong><code>PHP_OUTPUT_HANDLER_CLEAN</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that the output buffer has been cleaned.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-final">
    <strong><code>PHP_OUTPUT_HANDLER_FINAL</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that this is the final output buffering operation.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-cont">
    <strong><code>PHP_OUTPUT_HANDLER_CONT</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that the buffer has been flushed, but output buffering will
     continue.
    </p>
    <p class="para">
     As of PHP 5.4, this is an alias for
     <strong><code>PHP_OUTPUT_HANDLER_WRITE</code></strong>.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-end">
    <strong><code>PHP_OUTPUT_HANDLER_END</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Indicates that output buffering has ended.
    </p>
    <p class="para">
     As of PHP 5.4, this is an alias for
     <strong><code>PHP_OUTPUT_HANDLER_FINAL</code></strong>.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-cleanable">
    <strong><code>PHP_OUTPUT_HANDLER_CLEANABLE</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Controls whether an output buffer created by
     <span class="function"><a href="function.ob-start.html" class="function">ob_start()</a></span> can be cleaned.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-flushable">
    <strong><code>PHP_OUTPUT_HANDLER_FLUSHABLE</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Controls whether an output buffer created by
     <span class="function"><a href="function.ob-start.html" class="function">ob_start()</a></span> can be flushed.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-removable">
    <strong><code>PHP_OUTPUT_HANDLER_REMOVABLE</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     Controls whether an output buffer created by
     <span class="function"><a href="function.ob-start.html" class="function">ob_start()</a></span> can be removed before the end of the script.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
  
   <dt id="constant.php-output-handler-stdflags">
    <strong><code>PHP_OUTPUT_HANDLER_STDFLAGS</code></strong>
     (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>)
   </dt>

   <dd>

    <p class="para">
     The default set of output buffer flags; currently equivalent to
     <strong><code>PHP_OUTPUT_HANDLER_CLEANABLE</code></strong> |
     <strong><code>PHP_OUTPUT_HANDLER_FLUSHABLE</code></strong> |
     <strong><code>PHP_OUTPUT_HANDLER_REMOVABLE</code></strong>.
    </p>
    <p class="para">
     Available since PHP 5.4.
    </p>
   </dd>

  
 </dl>

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